This research study explores whether a beta-blocker can prevent a person from becoming more sensitive to pain after administration of an opioid. Beta blockers inhibit the sympathetic (fight or flight) response and are often used to treat angina and high blood pressure. In a previous study in human volunteers, the investigators demonstrated an increased sensitivity to pain after a 60-minute infusion of the opioid remifentanil. The goal of this study is to identify a possible inhibitor of this phenomenon.